Lecture 1

Question 1

6 Needs for rumen motility

Answer 1

1. Inoculate ingest with bacteria and protozoa
2. Mix saliva and ingesta to buffer acids produced by VFAs
3. Elimination of gas produced by bacteria
4. Prevent local accumulation of VFA at site of production
5. Assist VFA absorption through rumen wall
6. Prevent impaction by moving small particles into the lower GIT (omasum, abomasum and beyond)

Question 2

Does the rumen have an intrinsic pacemaker?

Answer 2

No

Question 3

If the rumen does not have intrinsic pacemaker, how does it have motility?

Answer 3

Innervated by Vagal Nerve

• multiple branches innervate different regions

Question 4

Which contraction is the vagal nerve responsible for in the rumen?

Answer 4

primary and secondary

Question 5

What does the vagal nerve affect in the motility of the rumen?

Answer 5

Frequency

Aplitude

Duration of motility

Question 6

What does the vagal nerve fire based upon?

Answer 6

Activity in the bilateral gastric centers of the medulla

Question 7

What type of autonomic response does the vagal nerve transmit to the rumen?

Answer 7

Parasympathetic

Question 8

Other than the vagal nerve innervation, what is another innervation of the rumen?

Answer 8

Splanchnic motor nerves - sympathetic

• inhibit motility

Question 9

3 Stimulatory inputs to gastric centres

Answer 9

1. Buccal mechanoreceptors (eating & chewing)
2. Tension receptors (high & low)
3. Epithelial (mucosal) receptors

Question 10

Affects of tension receptors

Answer 10

Low tension receptors - increase motility

High tension receptors - stop motility

Question 11

5 inhibitory inputs to gastric centers

Answer 11

1. High threshold tension receptors in reticulum and rumen
2. Tension receptors in abomasum
3. Epithelial receptors in rumen (pH)
4. Pain
5. Drugs (alpha-2 agonsits)

Question 12

What do tension receptors in rumen cause?

Answer 12

Both increase and decrease rumen motility

Question 13

2 type of epithelial Receptors

Answer 13

Mechanical

Chemical

Question 14

What will acid in abomasum do?

Answer 14

Causes stimulatory signals to increase rumen motility

Question 15

Explain the primary cycle of rumen motility

Answer 15

Major mixing contraction of ruminoreticulum

Last about 20 secs

Series of events

• Double contraction of reticulum
• Contraction of dorsal rumen sac (cranial to caudal)
• Contraction of ventral rumen sac (crainal to caudal and then caudal to cranial)

Occurs approx once/min

LOUD

Question 16

What does frequency of primary cycle depend upon?

Answer 16

Eating: 35-45 secs

Resting: 60-90secs

Ruminating: 45-60 secs

Question 17

How do we measure rumen motility through the fistula?

Answer 17

3 Catheters (attached to pressure transducer)

• One into the reticulum
• One under the mat in the dorsal sac
• One in the ventral sac

Connect to polygraph to measure pressure changes